This invention relates to a shearing machine for metal sheet having blades at right angles consisting of mutually movable segments.
The most commonly used shearing machines have a pair of rectilinear blades, whose motion causes cutting of an interposed metal sheet. In this case the cut can only be passing through, that is from one edge of the metal sheet to the opposite one.
A type of shearing machine is known whose blades are square shaped, i.e. consisting of two segments at right angles. In this case the cut is not necessarily running from one edge to the opposite one, but it can run also from one edge to a contiguous one.
Therefore the such a shearing machine with blade segments at right angles to each other has a greater flexibility and can afford better results as far as the minimization of the off-cuts is concerned.
A known improvement of this last type of shearing machine comprises having placed two shear-blades inclined relative to each other and operating the slide that supports the movable blade with two different stroke lengths, which can be selected, i. e. a smaller one which engages with the metal sheet only one of the two segments of the blade and the bigger one which engages both of them.
In this way, by means of a sequence of shorter strokes of the movable blade, the first of the two segments is able to execute a sequence of aligned (cuts) meanwhile the metal sheet is advancing parallely to said segment) before a longer final stroke of the same movable blade ends, by engaging also the second segment, the above-mentioned sequence of cuts by means of a transversal cut. With this system the above-mentioned first segment is thus able to execute cuts of a length longer than its own longitudinal extension.
The same operation can not be performed by the second segment as repeated cuts by the last-one would be unavoidably accompanied by unwanted contemporaneous cuts by the first segment.